1010: [HNOI2008]玩具装箱toy
第一次写斜率优化。。。首先一定要记住最好不用除法，因为会有精度误差=，=。。。。
4 #include<iostream> 5 #include<cstdlib> 6 #include<cmath> 7 #include<cstring> 8 #include<cstdio> 9 #include<algorithm> 10 #include<string> 11 #include<map> 12 #include<queue> 13 #include<vector> 14 #include<set> 15 #define inf 1000000000 16 #define maxn 50000+10 17 #define maxm 10000+5 18 #define eps 1e-10 19 #define ll long long 20 #define for0(i,n) for(int i=0;i<=(n);i++) 21 #define for1(i,n) for(int i=1;i<=(n);i++) 22 #define for2(i,x,y) for(int i=(x);i<=(y);i++) 23 #define for3(i,x,y) for(int i=(x);i>=(y);i--) 24 #define for4(i,x) for(int i=head[x],y=e[i].go;i;i=e[i].next,y=e[i].go) 25 using namespace std; 26 ll c[maxn],f[maxn],q[maxn];int tmp; 27 int read(){ 28 int x=0,f=1;char ch=getchar(); 29 while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();} 30 while(ch>='0'&&ch<='9'){x=10*x+ch-'0';ch=getchar();} 31 return x*f; 32 } 33 ll G(int a,int b) { 34 return (f[a]+(c[a]+tmp)*(c[a]+tmp)-f[b]-(c[b]+tmp)*(c[b]+tmp)); 35 } 36 ll S(int a,int b) { 37 return (2*(c[a]-c[b])); 38 } 39 int main(){ 40 //freopen("input.txt","r",stdin); 41 //freopen("output.txt","w",stdout); 42 int n=read(),l=read();tmp=l+1; 43 for1(i,n)c[i]=read()+c[i-1]; 44 for1(i,n)c[i]+=i; 45 int head=0,tail=0; 46 q[tail++]=0; 47 for1(i,n){ 48 while(head<tail-1&&G(q[head+1],q[head])<=c[i]*S(q[head+1],q[head]))++head; 49 int x=q[head]; 50 f[i]=f[x]+(c[i]-c[x]-tmp)*(c[i]-c[x]-tmp); 51 q[tail++]=i; 52 for(int j=tail-2;j>head;--j){ 53 int z=q[j+1],y=q[j],x=q[j-1]; 54 if(!(G(y,x)*S(z,y)<G(z,y)*S(y,x)))q[j]=q[--tail]; 55 else break; 56 } 57 } 58 cout<<f[n]; 59 return 0; 60 }
请看这份题解：http://www.cnblogs.com/perseawe/archive/2012/05/12/BZ1010.html
